It is well known to suspend a cover over a crop to prevent damage by frost, to control sunlight or for other reasons. These coverings or curtains may be in the form of long sheets, or webs, which are suspended by rows of hooks from suspension wires. The hooks in each row are attached to a continuous band, and a series of bands are sewn in spaced parallel relationship to an underlying sheet material which forms the body of the cover.
At present these covers may be made by sewing the bands in place by hand and subsequently inserting the suspension hooks, a laborious task when producing a cover, or series of covers, for thousands of square feet of fields. As a suspension wire is eventually to pass through a series of hooks, each band must be sewn in a straight line. Moreover since the curtain cannot be held taught when deployed it will inevitably sag and form troughs between adjacent hooks. If the cover is to hang evenly and straight without twists or uneven stress, the spacing between successive hooks must be uniform and the hooks in adjacent rows must be aligned in a direction normal to the bands. Thus it is advantageous to be able to fasten the hooks to the cover not only quickly, so that covers of reasonable size can be made efficiently, but also with the requisite alignment.
It is therefore an object of the present invention to provide an apparatus and method in which the above desideratum are attained.